Topband: The "Magic-T" vs 0 degree and 180 degree hybrid combiner/splitters

[Lee STRAHAN]

Hi All,
    Rick I have to agree with you up to a point. Your 9 circle and other 8 circle receiving arrays except mine are on wide footprints and only use 4 active antennas at a time. All of my antennas are reduced footprint antenna arrays which require much more phasing accuracy for optimum performance. In a small array such as a 4-square there is a need for at least 2 combining channels before a final combination. Many more in the all active 8 element array. Some with delay lines and some without. If you accurately measure a Magic Tee or an inverting transformer or even a 2:1 impedance matching transformer at 160 meters you will find that each one of these has a finite degree or 2 of phase shift. Fortunately this phase shift closely scales with frequency. I have not tried to fully understand why except they do indeed have line length. What is important is I have learned to use various combinations of the Magic Tee and the matching transformers, or inverters to my advantage in balancing the intrinsic phase shift between the inputs and delay lines improving the accuracy of the phasing over a broad range of frequencies. Sometimes the transformers are introduced into a phasing channel where one is not necessarily needed just to balance the phasing. Past conventional thinking about antennas was that if you could get 20 dB of front to back ratio on any array you were doing good. In my arrays with lots of front to back ratio (not all models)  this attention to detail of phasing almost always produces 30 dB of front to back ratio and when combined with new version more accurate element amplifiers I am getting reports of 40 dB front to back 
 So sometimes what looks unneeded and out of place may not be just because it looks out of place.
  Lee  K7TJR  OR
    


I often see 8 circle phasing networks that use a 3 piece ensemble of separate magnetic parts, consisting of:

1.  A 1:1 transformer wired for a 180 degree phase shift 2.  A 0 degree hybrid ("magic-tee"), and 3.  A 37.5 ohm to 75 ohm transformer.

A single 180 degree hybrid replaces all 3 of the above.
(There is nothing "incorrect" about the 3 piece ensemble; it's just needlessly complicated).

My 9 circle array uses this very successfully.

73
Rick N6RK
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